During the trip you will make lots of friends. Every place you visit you will meet new people whom you most likely meet again. This way you meet lot of people. At your birthday you invite the people who are at the same place at the same time. For me this was a little weird, because you don't know who will come at your party. At my party the crew of four boats came. I also celebrated my birthday a little later or earlier with friends who could not be there on my birthday itself.